Transatomic Power in Cambridge, Massachusetts, has designed a nuclear reactor, which is passively fail safe and can burn nuclear waste. They calculate that there is enough nuclear waste in storage, globally, to supply humanity's energy needs for the next 72 years. It is a Waste Annihilating Molten Salt (WAMS) reactor.

They dissolve spent fuel rods in hot liquid lithium fluoride. The uranium and plutonium present are concentrated to the point where they undergo fission, creating heat that operates via a heat exchanger to turn water to steam for driving turbines. The reactor vessel sits over a larger, heat dissipating vessel, with a plug in between tat melts if temperatures rise any higher. This means that a melt down is not possible, since the hot liquid will drop into the dissipating tank.

Within 5 years, the company plans to have a small reactor built, which could fit inside a shipping container, and be fully fail safe.

This is not the only game in town. A small travelling wave reactor is under development by TerraPower of Bellevue, Washington. And Toshiba/westinghouse have a cylindrical reactor design ready for small town use.

Hopefully, these carbon-free energy sources will be ready for use in a few years. I would like to see them being used to power commercial shipping.

Terrapower is one of Bill Gates' projects. The idea seems to make good sense and seems feasable as a power supply for cities and even towns.
The Terrapower version is actually a standing wave instead of a moving wave because their design manages the location of the reaction front by moving the fuel cores to keep the reaction in the center of the pile.
It is not a very cheap way of producing power but it should at least be competitive with the cost of other nuclear power generators.

I seriously doubt if a wave reactor can be made small enough to power a ship though because it requires a fairly large mass of low grade fuel to power the reaction.
One of the ideas floated in Canada was to build them (CANDLE) inside of the mine tunnels being proposed for spent fuel storage.